5i'
7.9 Other terminal equipments
Recommendation G.791
GENERAL CONSIDERATIONS ON TRANSMULTIPLEXING EQUIPMENTS
(Geneva, 1980; further amended)
The CCITT,
considering
the advantages offered in some cases by direct
through-connection (without voice-frequency interfaces) from FDM
signals to TDM signals and vice versa,
recommends in such cases
(1) the use of the transmultiplexing equipment described in
Definition 4020 of Recommendation G.701;
(2) Recommendation G.792 which contains the characteristics
common to all transmultiplexing equipment;
(3) Recommendation G.793 which concerns 60-channel transmulti-
plexers providing 2048 kbit/s signals and using A-law encoding;
(4) Recommendation G.794 which concerns 24-channel transmulti-
plexers providing 1544 kbit/s signals and using u-law encoding.
1 Complementary definitions
1.1 type P transmultiplexer (TMUX-P)
A transmultiplexing equipment in which the analogue interface
is made up of several groups.
1.2 type S transmultiplexer (TMUX-S)
A transmultiplexing equipment in which the analogue interface
is made up of one or more supergroups.
1.3 hierarchical transmultiplexer
A transmultiplexer in which the digital interfaces satisfy the
provisions of Recommendations G.703 and G.704 and the analogue
interfaces those of Recommendation G.233 [1].
1.4 transmultiplexer channel
A frequency band of 4000 Hz on the analogue side, correspond-
ing to a bit rate of 64 kbit/s on the digital side, which permits
the transmission of a signal limited to the telephone band
300-3400 Hz. Access may be gained to a given channel:
- either at the level of the time slot associated
with the relevant channel of the TDM signal;
- or at the level of the frequency band ( fp, fp_ |
000 Hz) of the FDM signal, fpbeing the virtual carrier frequency
associated with the channel concerned. The + sign corresponds to
the case of the base supergroup, the - sign to the case of the base
group.
Note - Correspondence between out-of-band signalling on the
analogue side and channel associated signalling on the digital side
will be covered in the Recommendations specific to the various
transmultiplexers.
2 Transmultiplexer application
The application on transmultiplexers for the interconnection
of digital and analogue networks is illustrated in Supplement
No. 28.
Reference
[1] CCITT Recommendation Recommendations concerning
translating equipments , Vol. III, Rec. G.233.
Recommendation G.792
CHARACTERISTICS COMMON TO ALL TRANSMULTIPLEXING EQUIPMENTS
(Geneva, 1980; further amended)
The CCITT,
recommends
that the characteristics below be respected by all the
transmultiplexing equipments defined in Recommendation G.791.
Recommendation O.133 contains information about test equip-
ment. Account should be taken of the measurement accuracy provided
by test equipment designed in accordance with that Recommendation.
The following specifications are based on ideal measuring
equipment. Therefore, they do not include any margin for measure-
ment errors.
To avoid level errors produced as a result of the use of test
frequencies which are sub-multiples of the PCM sampling rate, the
use of integer sub-multiples of 8 kHz should be avoided.
Where a nominal reference frequency of 1020 Hz is indicated
(measurement of attenuation/frequency distortion and adjustment of
relative levels), the actual frequency should be 1020, +2 to -7 Hz
in accordance with Recommendation O.6 [18].
1 Coding law
Transmultiplexers should satisfy Recommendation G.711, S 3.
2 Sampling rate of PCM channels
The nominal sampling rate of PCM channels is 8000 Hz _ |
0 x 10DlF2616 according to Recommendation G.711, S 2.
3 Amplitude limitation of PCM channels
In accordance with Recommendation G.711, S 4, the theoretical
load capacity of PCM channel is +3.14 dBm0 for the A-law and
+3.17 dBm0 for the u-law.
4 Accuracy of the analogue virtual carriers
The analogue virtual carriers should satisfy the Recommenda-
tion cited in [1].
5 Saturation level at the input of the analogue group
The transmultiplexers should be able to accept at their analo-
gue inputs, levels corresponding to the equivalent peak powers
defined in Table 3/G.223 [5] (for example, +19 dBm0 for a group and
+20.8 dBm0 for a supergroup).
Note - Attention is drawn to the possibility of using a
transmultiplexer on the interpolated side of a digital speech
interpolation (DSI) device. Given an interpolation rate of 2, this
would lead to equivalent peak powers of 19.5 dBm0 for TMUX-P and
21.2 dBm0 for TMUX-S (see Table 3/G.223 [5]).
6 Methods of measuring quality in the audio band
The various possible methods of measuring quality characteris-
tics in the audio band are indicated in Figure 1/G.792.
figure 1/G.792 p. 1
When method B cannot be used because it requires digital sig-
nal generators and analyzers, which certain Administrations do not
yet possess, method C can be used provisionally [looping of the
digital ports, use of the terminals of auxiliary analogue channels
(and possibly group modulators), assumption of the additivity of
impairments and deduction of the impairments at the terminals of
the channels (and possibly modulators) previously measured].
Method D corresponds in fact to four possible methods, depend-
ing on whether the emission of the test signal and its detection
takes place on the analogue side or the digital side.
Methods E and F are used for crosstalk measurements
For the sake of the convenience and precision of the measure-
ments, it is desirable that the regulation, when included in the
transmultiplexer, can be blocked with a gain equal to unity. The
specifications in SS 7 to 23 assume such blocking.
7 Attenuation distortion in the voice-frequency band as a function
of frequency
The measuring method is method A.
The variation of the attenuation of each channel of a
transmultiplexer as a function of frequency must remain within the
limits of the mask in Figure 2/G.792. The level of emission is
-10 dBm0; the reference frequency is 1020 Hz.
8 Group delay
8.1 Absolute value of the group delay
The measuring method is method A.
The absolute value of group delay defined as the minimum value
of group delay in the speech band 300-3400 Hz should remain less
than 3 ms for all the channels of a transmultiplexer.
Note - When the transmultiplexer is used for satellite digi-
tal communication at the earth station the minimum value of the
group propagation time in the audiofrequency band may be increased
from 3 ms to 6.5 ms. In all other cases, the value of 3 ms should
be complied with.
figure 2/G.792 p. 2
8.2 Group-delay distortion
The measuring method is method A.
The group-delay distortion should not exceed the limits of the
mask in Figure 3/G.792.
The minimum group delay is taken as a reference; the power
level at the input is 0 dBm0.
Figure 3/G.792, p.
9 Noise
9.1 Idle channel noise , with all channels idle
The measuring method is method B.
When a PCM signal corresponding to amplitude 0 for the u-law
and the number 1 for the A-law in all channels of the transmulti-
plexer is applied to the digital input of the transmultiplexer, the
psophometric noise measured over any channel at the digital output
should not exceed -65 dBm0p. The measurement is conducted in the
presence of pilots.
9.2 Channel noise, with all channels loaded except the one
measured
The measuring method is method A. In this case an intermodula-
tion measuring set-up using the white noise method is employed, as
described in the Recommendation cited in [6].
The level of emission of the noise signal being equal to the
conventional load of the FDM signal considered (the Recommendation
cited in [7]: 3.3 dBm0 for the group, 6.1 dBm0 for the supergroup),
the noise measured in any given measuring slot should not exceed
-62.5 dBm0p (i.e., -60 dBm0 in a 3100 Hz band).
The centre frequencies of the specified measuring slots (CCITT
Recommendation G.230 [8] and CCIR Recommendation 482 [9]) applica-
ble to the transmultiplexers are:
- for the base group: 70 and 98 kHz
- for the base supergroup: 394 and 534 kHz.
This measurement is carried out without emitting pilots or
out-of-band signalling.
Note - Attention is drawn to the possibility of using a
transmultiplexer on the interpolated side of a digital speech
interpolation (DSI) device. Given an interpolation rate of 2, this
would lead to conventional loads of 4.5 dBm0 for TMUX-P and
7.3 dBm0 for TMUX-S (see Table 2/G.223, [7]).
9.3 Single frequency noise outside the band 300-3400 Hz
The measuring method is B.
When a PCM signal corresponding to amplitude 0 for the u-law
and amplitude 1 for the A-law in all channels is applied to the
digital input of the transmultiplexer, the noise over any frequency
should not exceed -50 dBm0 with the exception of the frequency of
80 Hz where it should not exceed -40 dBm0.
9.4 Idle noise in the PCM - FDM direction all channels idle
The measuring method is method D. A PCM signal, amplitude 0
for the u-law and 1 for the A-law is applied at the digital input
of the transmultiplexer in all channels. The power of the noise
measured at the analogue output in any channel must be less than
-70 dBm0p.
Note - White noise is assumed, and to take account of the
psophometric weighting, the measurement can be made in a band of
1740 Hz, centred on the odd multiples of 2 kHz. The measurement may
be difficult in certain channels due to the presence of pilots.
10 Intermodulation
The measuring method is method A.
If two sine-wave signals of different frequencies
f1and f2belonging to the band 300-3400 Hz of the channel con-
sidered, having no harmonic relation and of equivalent levels in
the -4 to -21 dBm0 range, are applied simultaneously to the analo-
gue ports of the transmultiplexer, there should be no intermodula-
tion product of the type 2 f1 - f2of a level higher than -35 dB
with respect to the level of one of the two input signals.
11 Total distortion including quantizing distortion
The measuring method is method B (or provisionally method C).
If method B is used, the test signal is generated digitally
and is therefore affected by theoretical quantizing distortion.
A choice between the two following methods is recommended:
Method 1
The signal-to-total distortion ratio measured according to
method 1 described in S 8 of Recommendation G.712 should respect
the mask of Figure 4/G.792. The mask is to be complied with by all
channels of the transmultiplexer.
Method 2
With a sine-wave signal at a frequency between 700 and 1100 Hz
or 350 and 550 Hz (e.g. 420 _ 20 Hz) (except for submultiples of
8 kHz) being applied in the channel concerned at the digital input
of the transmultiplexer, the ratio of signal-to-total distortion
power, measured with appropriate noise weighting (see the Recommen-
dation cited in [10]), should be below the limits of the mask
represented in Figure 5/G.792. The mask is to be complied with by
all the channels of the transmultiplexer.
12 In-band spurious signals
The measuring method is method A.
The transmultiplexers must meet the provisions of
Recommendation G.712, S 9.
13 Variation of gain with the input level
The measuring method is method A, the pilots being present at
the analogue input.
With a sine-wave signal at a frequency between 700 and 1100 Hz
(except for submultiples of 8 kHz) and a level between -55 and
+3 dBm0 being applied in the channel concerned at the analogue
input of the transmultiplexer, the variation of gain with respect
to its value for an input level of -10 dBm0 should remain between
the limits of the mask shown in Figure 6/G.792. The mask is to be
complied with by all channels of a transmultiplexer.
figure 4/G.792 p. 4
figure 5/G.792 p. 4
figure 6/G.792 p. 6
14 Crosstalk
For measuring crosstalk, two transmultiplexers must be con-
nected back-to-back (methods E and F). There are two possible con-
figurations and four possible measurements (see Figure 7/G.792):
- far-end crosstalk digital to digital (see Note 1)
- near-end crosstalk digital to digital (see Note
1)
- far-end crosstalk analogue to analogue
- near-end crosstalk analogue to analogue
14.1 Intelligible crosstalk
When a sine-wave signal between 700 and 1100 Hz and with a
level of 0 dBm0 is injected in any channel on the digital or analo-
gue side of the transmultiplexer, the crosstalk ratio between the
signal channel and any other channel must be greater than 65 dB for
any of the four crosstalk contributions identified above (see
Note 2).
14.2 Unintelligible crosstalk
When a conventional telephone signal according to
Recommendation G.227 [11], is injected in any channel on the digi-
tal or analogue side of the transmultiplexer, at a level of 0 dBm0,
the level of crosstalk measured in any other channel for any of the
four crosstalk contributions identified above must be below
-60 dBm0p (see Note 3).
Note 1 - In this configuration, the two transmultiplexers are
connected at the level of the analogue FDM signal and there will
generally be a problem of level adaptation between the send and the
receive sides. This can be solved with the use of attenuators or
amplifiers of appropriate gain. Attention must be given on the risk
of introduction of additional crosstalk in these complementary dev-
ices. It should be desirable to include the level adaptation facil-
ities in the transmultiplexer itself.
Note 2 - In order to overcome fundamental gain enhancement
effects associated with PCM encoders, which can mask the true
crosstalk, measuring methods using activating signals based on
those defined in Recommendation G.712 can be used.
Note 3 - Recognizing the difficulty of generating conven-
tional telephone signals according to Recommendation G.227 in a
suitable format for insertion into either the analogue or digital
input to the transmultiplexer, it shall be adequate to demonstrate,
via suitable single frequency crosstalk tests, that the intent of
the above specification is met, without actually using a conven-
tional telephone signal.
Figure 7/G.972, p.
15 Go-to-return crosstalk
For measuring go-to-return crosstalk, two transmultiplexers
must be connected back-to-back (methods E and F). There are two
possible configurations and two possible measurements (see Figure
7b/G.792):
- near-end crosstalk digital to digital (see Note 1
of S 14);
- near-end crosstalk analogue to analogue.
When a sine-wave signal between 300 and 3400 Hz and with a
level of 0 dBm0 is injected in any channel on the digital or analo-
gue side of the transmultiplexer, the crosstalk ratio between the
signal channel and the associated return channel must be greater
than 58 dB for each contribution identified above.
When using method F, a PCM signal corresponding to amplitude 0
for the u-law and amplitude 1 for the A-law, should be inserted
into the digital input of all return channels.
Note - Concerning the activating signal for method F, see
Recommendation G.712, S 10.
16 Variation of the equivalent of the channels within the FDM
assembly
Measuring method A.
When a test tone at the equivalent of 1020 Hz in any channel,
and with a level of -10 dBm0 is applied to the analogue input of
the transmultiplexer, the level measured at the analogue output of
the transmultiplexer shall be within a tolerance of _ | dB of the
level measured when that test tone is applied at the equivalent of
1020 Hz in the channel containing the reference pilot of the FDM
assembly considered.
17 Adjustment of the relation between the coding law and the
analogue level
Measuring method D.
To measure the correspondence between the coding laws and the
analogue levels, the sequence of character signals from
Table 5/G.711 for the A-law and from Table 6/G.711 for the u-law
may be applied periodically at the digital input of the transmulti-
plexer: the signal at the analogue output of the transmultiplexer
should correspond to a sine-wave signal of frequency 1 kHz in the
corresponding channel at a level between -0.5 and +0.5 dBm0.
Note - The use of another digital periodic sequence
representing a nominal reference frequency of 1020 Hz at a nominal
level of 0 dBmO is acceptable, provided that the theoretical level
accuracy is better than _ | .03 dB.
To check the load capacity of the PCM coder contained in the
transmultiplexer, a sine-wave signal at a nominal frequency of
1020 Hz can be applied for any channel at the analogue input of
the transmultiplexer. Initially the level of this signal is consid-
erably below the load capacity, then it is raised gradually. Note
is taken of the input level at which the character signal
corresponding to the extreme quantization interval for positive and
negative amplitudes first appears at the digital output in the
channel considered. The load capacity is then taken to be equal to
this input level, increased by 0.3 dB. The values obtained for the
various channels should be between 2.64 and 3.64 dBm0 for the A-law
and between 2.67 and 3.67 dBm0 for the u-law.
18 Carrier leak at the analogue ports
Measuring method A, the analogue input of the transmultiplexer
being looped to its nominal impedance.
The transmultiplexers should meet the provisions of the Recom-
mendation cited in [12].
19 Protection against out-of-band signals at the analogue ports
19.1 Out-of-band spurious signals at the analogue output
The measuring method is C for the TMUX-P, range a) (see
below), otherwise A. The test signal has a level of 0 dBm0. For the
TMUX-P, range a), a signal according to Recommendation G.227 is
used, otherwise a sine-wave signal (300 to 3400 Hz). The level of
supurious signals outside the group or supergroup band ( f1to f2)
at the analogue output should not exceed the following limits:
TMUX-P a) f1 > fx > ( f1- 4 kHz) -
60 dBm0p
and
f2 < fx < ( f2 + 4 kHz) (Note 1)
b) ( f1 - 4 kHz) > fx > ( f1- 12 kHz) -
70 dBm0
and
( f2 + 4 kHz) < fx < ( f2+ 12 kHz) (Note 2)
c) fx ( f1 - 12 kHz)
and -80 dBm0
fx _" ( f2 + 12 kHz)
TMUX-S a) fx = f1 - 4 kHz -60 dBm0
and
fx = f2 + 4 kHz (Note 3)
b) ( f1 - 8 kHz) > fx > ( f1- 20 kHz) -
70 dBm0
and
( f2 + 8 kHz) < fx < ( f2+ 20 kHz) (Note 2)
c) fx ( f1 - 20 kHz)
and -80 dBm0
fx _" ( f2 + 20 kHz)
Note 1 - Telephony channels, pilots or additional test fre-
quencies are possible in this frequency range.
Note 2 - Adjacent carrier-frequency sound-programme channels
may begin in this range (with reduced requirements).
Note 3 - This range may contain pilots or additional measur-
ing frequencies.
19.2 Crosstalk due to out-of-band signals at the analogue
input
Measuring methods C and A, respectively (see S 19.1). With
test signals as in S 19.1 in a channel of an adjacent FDM assembly,
the level at the transmultiplexer output should not exceed the fol-
lowing limits:
TMUX-P a) f1 > fx > ( f1- 4 kHz) -60
dBm0p
and
f2 < fx < ( f2 + 4 kHz) (Note)
b) fx < ( f1 - 4 kHz) -70 dBm0
and
fx > ( f2 + 4 kHz) (Note)
TMUX-S a) fx = f1 - 4 kHz -50 dBm0
and
fx = f2 + 4 kHz (Note)
b) fx < ( f1 - 8 kHz) -70 dBm0
and
fx > ( f2 + 8 kHz) (Note)
Note - For this measurement, a low-level auxiliary signal is
injected into the disturbed channel. The appropriate auxiliary sig-
nal is a sine-wave signal between -33 and -40 dBm0. The frequency
and characteristics of the filter in the measuring equipment must
be carefully selected to ensure that the auxiliary signal does not
appreciably reduce the accuracy of the crosstalk measurement.
20 Protection and suppression of pilots
Measuring method D.
The transmultiplexers should meet the provisions of the Recom-
mendation cited in [14].
21 Protection and suppression of out-of-band signalling
21.1 Protection of the out-of-band signalling channel for
transmultiplexers using signalling system R2
Measuring method D.
When a transmultiplexer is capable of emitting out-of-band
signalling waves at frequency 3825 Hz, it should meet the provi-
sions of Recommendation Q.414 [15], Figure 6/Q.414 being replaced
by Figure 7/G.792. The measuring method associated with the latter
figure is recalled in Note 1.
Note 1 - The signalling channel must be protected at the
sending end against disturbance from the associated and the adja-
cent channel.
When a sine-wave at 0 dBm0 level is applied to the digital input of
the associated channel, the level measured at the analogue output
of the transmultiplexer must not exceed the levels shown in
Figure 8/G.792.
When a sine-wave of frequency f is applied to the digital input of
the adjacent channel, it produces two signals that appear on the
frequency scale of Figure 8/G.792 as having the frequencies
(4000 + f ) and (4000 - f ). The level of the (4000 + f ) signal
measured at the analogue output of the transmultiplexer shall not
be higher than -33 dBm0, when the sine-wave with frequency f is
applied to the digital input of the adjacent channel at a level
shown in Figure 8/G.792 for the frequency of (4000 + f ). The level
of the (4000 - f ) signal, measured at the analogue output of the
transmultiplexer, shall not be higher than -33 dBm0, when the
sine-wave with frequency f is applied to the digital input of the
adjacent channel at any level below the value shown in
Figure 8/G.792 for the frequency (4000 - f ).
21.2 Disturbance of telephone channels by out-of-band sig-
nalling frequency for transmultiplexers using signalling system R2
The measuring method is method B or D.
Interference at 175 Hz and 3825 Hz should not exceed -53 dBm0
respectively -63 dBm0 when a continuous tone of 3825 Hz with a nom-
inal level of -20 dBm0 is applied to all channels. These values
correspond to a contribution to the channel noise in the order of
-73 dBm0p (design objective).
Figure 8/G.792, p.
21.3 Other out-of-band signalling systems
See Annex A.
22 Mutual interference between pilots and out-of-band signalling
The transmultiplexers capable of emitting and receiving
out-of-band signalling should meet the provisions of the Recommen-
dation cited in [17].
23 Short- and long-term variation of loss with time
The measuring method is A. When a sine-wave signal at level
-10 dBm0 and at a nominal frequency of 1020 Hz is applied at the
analogue input of the transmultiplexer, the level measured at the
analogue output should not vary by more than _ | .2 dB during
10 consecutive minutes of normal operation, more than _ | .5 dB
during 3 consecutive days nor by more than _ | dB for one year,
allowing for the authorized variations of power supply, voltages
and temperature.
ANNEX A
(to Recommendation G.792)
Out-of-band signalling systems using a burst-mode method
The possibility of such systems is mentioned in Annex A to
Recommendation Q.21 and Annex B to Recommendation G.232. These
annexes should be taken into consideration. When a transmultiplexer
is capable of converting such systems, the following applies:
- Signalling frequency at the sending point:
3825 Hz _ 4 Hz.
- Send level of the signalling frequency: -5
dBm0 _ 1 dB.
- Protection of the out-of-band signalling channel:
see Figure 8/G.792.
- Disturbance of telephone channels by the
out-of-band signalling frequency: the measuring method is method B.
- Channel noise should not exceed -63 dBm0p in the
call channel (continuous tone).
- In the adjacent channel (the closest to the sig-
nalling frequency) likewise -63 dBm0p burst or continuous tone.
- In every other channel -76 dBm0p burst or con-
tinuous tone.
Note 1 - Burst tones do not occur in the call channel after
call set-up has taken place.
Note 2 - Burst rates are in the order of 10 to 25 Hz.
Note 3 - Charge metering pulses are of long duration, e.g.
150/450 ms and are evaluated as a continuous tone.
References
[1] CCITT Recommendation Recommendations relating to the
accuracy of carrier frequencies , Vol. III, Rec. G.225, S 1.
[2] CCITT Recommendation Pilots on groups, supergroups,
etc. , Vol. III, Rec. G.241, S 1.
[3] Ibid. , S 2.
[4] Ibid. , S 3.
[5] CCITT Recommendation Assumptions for the calculation of
noise on hypothetical reference circuits for telephony , Vol. III,
Rec. G.223, Table 3/G.223, S 6.
[6] CCITT Recommendation Measurement of circuit noise in
cable systems using a uniform-spectrum random noise loading ,
Vol. III, Rec. G.228, SS A.1, A.2.2.
[7] CCITT Recommendation Assumptions for the calculation of
noise on hypothetical reference circuits for telephony , Vol. III,
Rec. G.223, S 2.1.
[8] CCITT Recommendation Measuring method and
through-connection filters for noise produced by modulating equip-
ment , Vol. III, Rec. G.230.
[9] CCIR Recommendation Measurement of performance by
means of a signal of a uniform spectrum for systems using
frequency-division multiplex telephony in the fixed satellite ser-
vice , Vol. IV, Rec. 482, ITU, Geneva, 1978.
[10] CCITT Recommendation Assumptions for the calculation
of noise on hypothetical reference circuits for telephony ,
Vol. III, Rec. G.223, S 7.
[11] CCITT Recommendation Conventional telephone signal ,
Vol. III, Rec. G.227.
[12] CCITT Recommendation 12-channel terminal equipments ,
Vol. III, Rec. G.232, SS 5.1, 5.2.
[13] CCITT Recommendation Through-connection of groups,
supergroups, etc. , Vol. III, Rec. G.242, S 1.
[14] CCITT Recommendation 12-channel terminal equipments ,
Vol. III, Rec. G.232, SS 12.1, 12.2 and Annex A.
[15] CCITT Recommendation Signal sender , Vol. VI,
Rec. Q.414, Figure 6/Q.414.
[16] CCITT Recommendation 12-channel terminal equipments ,
Vol. III, Rec. G.232.
[17] Ibid. , S 12.3 and Annex B.
[18] CCITT Recommendation 1020 Hz reference test frequency
, Vol. IV, Rec. O.6.
Recommendation G.793
CHARACTERISTICS OF 60-CHANNEL TRANSMULTIPLEXING EQUIPMENTS
(Geneva, 1980; further amended)
1 Introduction
The 60-channel transmultiplexer is a transmultiplexing equip-
ment which satisfies Recommendations G.791 and G.792 and provides
interconnection between two digital signals at 2048 kbit/s and an
analogue supergroup (60-channel TMUX-S).
2 Digital interfaces
2.1 Coding law
The coding law used is A-law specified in
Recommendation G.711.
2.2 Interfaces
The 2048-kbit/s interfaces satisfy Recommendation G.703, S 6.
2.3 Frame structure
The structure is specified in Recommendation G.704, S 3.3.1.
The strategy and the criteria for loss and recovery of frame
alignment satisfy Recommendation G.706, S 4.1.
2.4 Multiframe structure
The multiframe structure of time slot 16 satisfies
Recommendation G.704, S 3.3.3.
The strategy and the criteria for loss and recovery of mul-
tiframe alignment satisfy Recommendation G.732, S 5.2.
3 Analogue interfaces
3.1 Ports
The analogue interface consists of a 60-channel supergroup
(band 312-552 kHz) which satisfies Recommendation G.233 [1].
The preferred signal levels at the supergroup distribution
frame should be:
- for sending -36 dBr
- for receiving -30 dBr
The impedances are: 75 ohms (unbalanced).
3.2 Pilots
The 60-channel transmultiplexer should transmit the following
pilots:
TMUX-S: A supergroup pilot with a frequency 411 |
20 Hz and a level of -20 dBm0,
one pilot per group with a level of -20 dBm0 and frequen-
cies of:
Group 1: 335 | 20 Hz
Group 2: 383 | 20 Hz
Group 3: 431 | 20 Hz
Group 4: 479 | 20 Hz
Group 5: 527 | 20 Hz
The transfer of pilot alarms individually for each group in a
supergroup and the consequence for the split channels of group 3
can be seen in Figure 1 of Supplement No. 32.
Other sets of pilots as recommended in Recommendation G.241
can be used. Special attention should be given to the compatibility
of the set of pilots adopted with the out-of-band signalling system
using a frequency at 3825 Hz.
The characteristics relating to the generation and transmis-
sion of these pilots are given in Recommendation G.241 [2].
3.3 Pilot detection and regulation
The transmultiplexer may or may not regulate levels on the
basis of the levels of the group and supergroup pilots. If so, the
transmultiplexer must meet the conditions of the Recommendation
cited in [2]. Detection of the levels of the group pilots and or
supergroup mentioned in S 3.2 should, however, be effected to
ensure operation of the interruption control system
(Recommendation Q.416 [3]), when R2 signalling is used.
4 Correspondence between analogue and digital channels
A fixed correspondence is established between the analogue and
digital channels. The correspondence shown in Table 1/G.793 (which
facilitates the transfer of alarms and results in a natural order
of the channels on the analogue side) is recommended.
H.T. [T1.793]
TABLE 1/G.793
_________________________________________________
PCM 1 channels 1 to 12 Group 1 312-360 kHz
_________________________________________________
PCM 1 channels 13 to 24 Group 2 360-408 kHz
_________________________________________________
PCM 1 channels 25 to 30 Group 3 408-432 kHz
_________________________________________________
PCM 2 channels 1 to 6 Group 3 432-456 kHz
_________________________________________________
PCM 2 channels 7 to 18 Group 4 456-504 kHz
_________________________________________________
PCM 2 channels 19 to 30 {
Group 5
504-552 kHz
}
_________________________________________________
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Note - In national networks or by agreement between Administra-
tions, other schemes of correspondence between analogue and digital
channels may be used.
Table 1/G.793 [T1.793], p.
5 Plesiochronous operation of incoming PCM streams
Sixty-channel transmultiplexers should be able to accept two
mutually plesiochronous incoming PCM streams within the limits laid
down in Recommendation G.703 (bit rate 2048 kbit/s, _ | 0 | (mu |
0DlF2616).
In the case of transmultiplexers with digital filtering, this
means that the two input ports at 2048 kbit/s are fitted with frame
aligners (jump or repetition of samples) and multiframe aligners
for synchronizing the incoming PCM streams with the transmulti-
plexer clock. In order to avoid a major slip frequency, the two
incoming PCM streams should be either synchronous with the
transmultiplexer or plesiochronous with each other and with the
transmultiplexer clock, so that Recommendation G.811 on the
plesiochronous network is satisfied.
6 Synchronization of transmultiplexer
The transmultiplexer must produce virtual analogue carrier
frequencies with the accuracy specified in Recommendation G.225 [4]
(_ | 0DlF2617).
For this purpose, it is recommended:
a) either that the transmultiplexer should have an
internal clock of sufficient accuracy;
b) or that the transmultiplexer should be syn-
chronizable with an external signal which may be:
1) a frequency (see Note 3) produced by a central
FDM generator: 4, 12 or 124 kHz;
2) or one of the incoming PCM streams which has
sufficient accuracy (this may be the case, for example, when this
PCM stream at 2048 kbit/s is produced by a TDM switching equip-
ment). If both 2048-kbit/s streams are of sufficient accuracy, the
use of PCM stream No. 1 is preferred. In most cases this avoids, at
the digital filtering transmultiplexer input, the slipping
phenomena which, when too frequent, cause high error rates on
in-band data signals.
Note 1 - In the case of a digital filtering transmultiplexer,
when synchronization on one of the incoming PCM streams is not pos-
sible, the remote digital terminal should have the sending side
synchronized with the receiving side so as to avoid slipping at the
transmultiplexer input.
Note 2 - In the case of external synchronization, transmulti-
plexers often have an internal oscillator locked to the external
signal. If, upon loss of the external sync signal, this internal
oscillator is allowed to continue to supply the clock for the out-
going digital signal (now in the free-running mode), then this
oscillator should have a minimum free-running accuracy of
50 x 10DlF2616. This is intended to allow the distant end digital
terminal to receive an adequate frequency for alarm purposes only,
so as not to confuse maintenance and trouble-shooting activities.
Also, a local alarm should be given in the event of a fault in the
synchronization system or in the absence of the external synchroni-
zation signal (Tables 2/G.793, 3/G.793 and 2 of Supplement No. 32).
Note 3 - In the case where the transmultiplexer is to be used
in a TDMA satellite application, the effect of the satellite
Doppler frequency variation must be taken into account. This can be
done in two ways:
- either, the TDMA terminal incorporates the
Doppler buffer memories of appropriate capacity in the earth sta-
tion to satellite direction. In this case, the two directions of
the TMUX must be synchronized from one of the two 2048 kbit/s PCM
streams transmitted by the TDMA receive terminal;
- or, the TDMA terminal does not incorporate
Doppler buffers. In this case, the PCM to FDM direction of the TMUX
may be synchronized from one of the two 2048 kbit/s streams
transmitted by the TDMA receive terminal. In the FDM to PCM direc-
tion, the 2048 kbit/s streams transmitted by the TMUX must be made
synchronous with the TDMA system transmit clock: this supposes that
a synchronization signal (contradirectional with the data) is pro-
vided by the TDMA transmit terminal to the TMUX. In the case where
the processing in a digital filtering transmultiplexer is made syn-
chronously for the two directions, Doppler buffer memories of
appropriate capacity must be incorporated in the PCM interfaces.
7 Signalling
Different kinds of signalling systems can be envisaged.
7.1 In-band signalling
The 60-channel transmultiplexer is transparent for
channel-associated in-band signalling.
7.2 Common channel signalling
In the case when common channel signalling must be routed
through the transmultiplexer, attention is drawn to the fact that
the transmission capabilities of a channel in the transmultiplexer
is limited to the band 300-3400 Hz (i.e. data rates corresponding
to this frequency band). Information on signalling bit rates is
given in S 2 of Recommendation Q.702.
In the opposite case, when common channel signalling is not
routed through the TMUX, no special problems are recognized.
7.3 Out-of-band signalling
As regards Signalling System R2, signalling conversion between
the analogue and digital versions of line signalling as recommended
in Recommendation Q.430 is to be used in the case of international
interconnection and should conform to the following specifications.
The transmultiplexer, or an additional equipment associated
with it, converts the analogue version to the 2-bit digital version
of the R2 line Signalling System, and vice versa. In all cases, the
transmultiplexer should provide the following facilities for sig-
nalling:
a) Analogue side
1) recognition of the signalling frequency at 3825
Hz in accordance with Recommendation Q.415 [5];
2) transmission of the signalling frequency at 3825
Hz in accordance with Recommendation Q.414 [6];
3) supervision of group pilots (and supergroup
pilots if necessary) in accordance with Recommendation Q.416 [3].
b) Digital side
1) extraction of signalling bits a and b of time
slots 16 received in accordance with the Recommendation cited
in [7];
2) insertion of appropriate signalling data in
bits a and b of time slots 16 transmitted in accordance with the
Recommendation cited in [7];
3) detection of PCM system faults.
The conversion between the analogue and digital versions of
the R2 line Signalling System should be made in accordance
with [8]. When the conversion is made in an external equipment, the
transmultiplexer should supply the necessary ports.
For national networks, a method of using the analogue line
signalling version on both analogue and digital transmission sys-
tems is described in Supplement No. 32.
8 Fault conditions and consequent action
8.1 Principles of the action to be taken
The principles governing the handling of alarms is as follows:
The behaviour of a transmultiplexer vis-a-vis a 30-channel PCM mul-
tiplex should be the same as that of another 30-channel PCM multi-
plex. However, the transmultiplexer performs certain functions
peculiar to digital multiplexing equipments such as the transmis-
sion of the Alarm Indication Signal (AIS). Vis-a-vis a group modu-
lator, it should behave like another group modulator.
The principles of alarm transfer are described in
Supplement No. 32 which also contains particular solution used in
national networks.
8.2 Digital version of R2 signalling system
Table 2/G.793 summarizes the fault conditions and the conse-
quent actions.
8.3 In-band signalling and common channel signalling
Table 3/G.793 summarizes the fault conditions and the conse-
quent actions (see Note).
Note - The problem of per channel alarm transfer needs
further study. For applications where the TMUX is used in TDMA con-
figuration, Recommendation Q.33 should be considered [11].
Blanc
H.T. [1T2.793]
________________________________________________________
TABLE 2/G.793
{
Fault conditions and consequent actions, applicable if
Signalling System R2 is used
(see Note 1)
}
________________________________________________________
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__________________________________________________________________________________________________________________________________________________________________________________________________________
Consequent actions
Fault conditions
{
__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 3) Yes Yes PCM > FDM a=b=1 (see Note 4) |
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__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of multiframe alignment
(see Note 2)
} Yes (see Note 3) Yes a=b=1 (see Note 4)
__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Reception of bit 3, time slot 0 or bit 6, time slot 16, frame 0
(see Note 2)
} a=b=1
{
Absence of the received group pilot
(see Note 5)
} Yes Yes FDM > PCM Absence of pilot Yes (see Note 6) |
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__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received supergroup pilot
(see Note 7)
} Yes Absence of pilot
__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm (Note 8)
} Yes
Failure of power supply Yes Yes, if possible Yes, if possible
__________________________________________________________________________________________________________________________________________________________________________________________________________
System failure (see Note 9) Yes Yes Yes (see Note 6)
__________________________________________________________________________________________________________________________________________________________________________________________________________
{
Synchronization failure
(see Note 10)
} Yes
__________________________________________________________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes
| n the table signifies that an action should be taken as a conse-
quence of the relevant fault conditions. An open space in the table
signifies that the relevant action should not be taken as a conse-
quence of the relevant fault condition, if this condition is the
only one present. If more than one fault condition is simultane-
ously present, the relevant action should be taken if, for at least
one of the conditions, a Yes is defined in relation to this action.
Pour Montage : System alarms FDM alarms PCM alarms
Table 2/G.793 [1T2.793] (a l'italienne), p.
H.T. [2T2.793]
Note 2 - The fault conditions "Loss of signal at 2 Mbit/s", "Error
ratio > 10DlF2613", "Loss of frame alignment", "Loss of multiframe
alignment", "Reception of bit 3, time slot 0", "Reception of bit 6,
time slot 16, frame 0" and the consequent action "Bit 3, time
slot 0 to 1", "Bit 6, time slot 16, frame 0 to 1", "Bit 6, time
slot 16, frame 0 to 1" and "AIS sent" are defined in
Recommendation G.732.
Note 3 - The 60-channel transmultiplexer should be able to detect
the alarm indication signal (AIS) on incoming streams at
2048 kbit/s. When AIS is detected, the prompt maintenance indica-
tion associated with the loss of frame alignment, with an excessive
error rate or with the loss of multiframe alignment should be
blocked.
Note 4 - This action is not necessary when the digital version of
Signalling System R2 is used, but may be useful with other applica-
tions.
Note 5 - The definition of absence of group pilot used for the
operation of the interruption control system is given in the Recom-
mendation cited in [9]. The supergroup pilot can also be used.
Note 6 - The AIS is sent only if the 30 channels of a single PCM
stream are in the alarm condition.
Note 7 - Detection of "absence of supergroup pilot" is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Note 8 - The concept of pilot level deviation alarm corresponds to
a variation on the level of the pilot from its nominal value by
more than _ | dB, as stated in [10]. This applies only to
transmultiplexers with automatic internal level regulation.
Note 9 - The "system" fault condition corresponds to a fault on
the transmultiplexer detected by the transmultiplexer's supervision
system, when it has one.
Note 10
- The "synchronization" fault is that mentionned in S 6 of
Recommendation G.793. When the transmultiplexer is synchronized
with an external signal or with one of two incoming PCM streams at
2048 kbit/s, the transmultiplexer should transmit an alarm signal
in the event of synchronization loss.
H.T. [1T3.793]
TABLE 3/G.793
Fault conditions and consequent actions, applicable for in-band
signalling and common channel signalling
(Note 1)
__________________________________________________________________________________________________________________________________________________________________
Consequent actions
|
Fault conditions {
__________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 3) Yes Yes PCM | > | DM Yes (see Note 4)
__________________________________________________________________________________________________________________________________________________________________
{
Absence of the received group pilot
(see Note 5)
} Yes Yes FDM | > | CM Yes (see Note 6) {
Absence of the received supergroup pilot
(see Note 7)
}
__________________________________________________________________________________________________________________________________________________________________
Yes {
Pilot level deviation alarm
(see Note 8)
} Yes
__________________________________________________________________________________________________________________________________________________________________
Failure of power supply Yes Yes, if possible Yes, if possible System failure (see Note 9)
__________________________________________________________________________________________________________________________________________________________________
Yes Yes, 5 groups Yes (see Note 7) {
Synchronization failure
(see Note 10)
} Yes
__________________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes in the table signifies that an action should be
taken as a consequence of the relevant fault conditions. An open
space in the table signifies that the relevant action should not be
taken as a consequence of the relevant fault condition, if this
condition is the only one present. If more than one fault condition
is simultaneously present, the relevant action should be taken if,
for at least one of the conditions, a Yes is defined in relation to
this action.
Note 2 - The fault conditions "Loss of signal at 2 Mbit/s", "Error
ratio > 10DlF2613", "Loss of frame alignment", and the consequent
action "Bit 3, time slot 0 to 1", and "AIS sent" are defined in
Recommendation G.732.
Note 3 - The 60-channel transmultiplexer should be able to detect
the alarm indication signal (AIS) on incoming streams at
2048 kbit/s. When AIS is detected, the prompt maintenance indica-
tion associated with the loss of frame alignment, with an excessive
error rate should be blocked.
Note 4 - In the PCM FDM direction, the pilots must be cut for the
3 groups associated with a PCM multiplex signal in the event of the
detection of a fault on the PCM multiplex signal stream. When a
single PCM multiplex signal is faulty, this involves the blocking
of 6 channels which are not faulty.
Note 5 - The definition of absence of group pilot used for the
operation of the interruption control system is given in the Recom-
mendation cited in [9]. The supergroup pilot can also be used.
Note 6 - The AIS is sent only if the 30 channels of a single PCM
stream are in the alarm condition.
Note 7 - Detection of "absence of supergroup pilot" is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Pour Montage : System alarms IDM alarms PCM alarms
Notes of the Table 2/G.793 [2T2.973], p.
H.T. [1T3.793]
TABLE 3/G.793
Fault conditions and consequent actions, applicable for
in-band signalling and common channel signalling
(Note 1)
__________________________________________________________________________________________________________________________________________________________________
Consequent actions
|
Fault conditions {
__________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 3) Yes Yes PCM | > | DM Yes (see Note 4)
__________________________________________________________________________________________________________________________________________________________________
{
Absence of the received group pilot
(see Note 5)
} Yes Yes FDM | > | CM Yes (see Note 6) {
Absence of the received supergroup pilot
(see Note 7)
}
__________________________________________________________________________________________________________________________________________________________________
Yes {
Pilot level deviation alarm
(see Note 8)
} Yes
__________________________________________________________________________________________________________________________________________________________________
Failure of power supply Yes Yes, if possible Yes, if possible System failure (see Note 9)
__________________________________________________________________________________________________________________________________________________________________
Yes Yes, 5 groups Yes (see Note 7) {
Synchronization failure
(see Note 10)
} Yes
__________________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes in the table signifies that an action should be
taken as a consequence of the relevant fault conditions. An open
space in the table signifies that the relevant action should not be
taken as a consequence of the relevant fault condition, if this
condition is the only one present. If more than one fault condition
is simultaneously present, the relevant action should be taken if,
for at least one of the conditions, a Yes is defined in relation to
this action.
Note 2 - The fault conditions "Loss of signal at 2 Mbit/s", "Error
ratio > 10DlF2613", "Loss of frame alignment", and the consequent
action "Bit 3, time slot 0 to 1", and "AIS sent" are defined in
Recommendation G.732.
Note 3 - The 60-channel transmultiplexer should be able to detect
the alarm indication signal (AIS) on incoming streams at
2048 kbit/s. When AIS is detected, the prompt maintenance indica-
tion associated with the loss of frame alignment, with an excessive
error rate should be blocked.
Note 4 - In the PCM FDM direction, the pilots must be cut for the
3 groups associated with a PCM multiplex signal in the event of the
detection of a fault on the PCM multiplex signal stream. When a
single PCM multiplex signal is faulty, this involves the blocking
of 6 channels which are not faulty.
Note 5 - The definition of absence of group pilot used for the
operation of the interruption control system is given in the Recom-
mendation cited in [9]. The supergroup pilot can also be used.
Note 6 - The AIS is sent only if the 30 channels of a single PCM
stream are in the alarm condition.
Note 7 - Detection of "absence of supergroup pilot" is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Pour Montage : System alarms IDM alarms PCM alarms
Table 3/G.793 [1T3.793], p.
H.T. [2T3.793]
Note 8 - The concept of pilot level deviation alarm corresponds to
a variation on the level of the pilot from its nominal value by
more than _ | dB as stated in the Recommendation cited in [10].
This applies only to transmultiplexers with automatic internal
level regulation.
Note 9 - The "system" fault condition corresponds to a fault on
the transmultiplexer detected by the transmultiplexer's supervision
system, when it has one.
Note 10 - The "synchronization" fault is that mentionned in S 6 of
the Recommendation G.793. When the transmultiplexer is synchronized
with an external signal or with one of the two incoming PCM streams
at 2048 kbit/s, the transmultiplexer should transmit an alarm sig-
nal in the event of synchronization loss.
Pour Montage : System alarms IDM alarms PCM alarms
H.T. [1T1.794]
TABLE 1/G.794
Fault conditions and consequent action for the
24-channel transmultiplexer
_________________________________________________________________________________________________________________________________________________________
{
Consequent
Action
Fault Conditions
} {
Prompt maintenance alarm indication (7)
} {
Alarm indication to the remote equipment (3)
} AIS sending (4) {
Blocking of faulty speech channels
} {
Pilot cut-off
to the remote
FDM terminal
}
{
Loss of frame alignment and multiframe alignment or
Loss of incoming signal (2)
} Yes (8) Yes Yes (PCM | > | DM) {
Digital error
ratio 10DlF2614
or 10DlF2613 (10)
}
_________________________________________________________________________________________________________________________________________________________
Yes (8) Yes {
Reception of alarm indication
from the remote equipment (2, 3)
} Yes AIS receiving (4)
_________________________________________________________________________________________________________________________________________________________
Yes Yes (PCM | | > | DM)
_________________________________________________________________________________________________________________________________________________________
Absence of group pilot (5) Yes Yes (9) Yes {
Pilot level deviation alarm (11)
}
_________________________________________________________________________________________________________________________________________________________
Yes, if regulation is present
_________________________________________________________________________________________________________________________________________________________
Failure of power supply (2) Yes {
Yes, depending
on network
applications
} System failure (6) Yes
_________________________________________________________________________________________________________________________________________________________
{
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} Synchronization failure Yes
_________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes in the table signifies that an action should be
taken as a consequence of the relevant fault conditions. An open
space in the table signifies that the relevant action should not be
taken as a consequence of the relevant fault condition, if this
condition is the only one present. If more than one fault condition
is simultaneously present, the relevant action should be taken if,
for at least one of the conditions, a Yes is defined in relation to
this action.
Note 2 - The fault conditions "Loss of incoming signal", "Loss of
frame alignment and multiframe alignment", "Reception of alarm
indication to the remote equipment" and "Failure of power supply"
are defined in Recommendation G.733.
Note 3 - For "Alarm indication to the remote equipment", data link
bits are used.
Note 4 - The AIS can be used only in the new frame structure to be
specified by Study Group XVIII.
Note 5 - The level, at which "Absence of group pilot" is detected,
is under study.
Note 6 - The "System failure", which is only for the digital
filtering transmultiplexer, corresponds to a fault detected by the
transmultiplexer's supervision system, when it has one.
Note 7 - The consequent action "Prompt maintenance Alarm indica-
tion" and "Alarm indication to the remote equipment" are defined in
Recommendation G.733.
Notes of the Table 3/G.793 [2T3.793], p.
References
[1] CCITT Recommendation Recommendations concerning
translating equipments , Vol. III, Rec. G.233.
[2] CCITT Recommendation Pilots on groups, supergroups,
etc. , Vol. III, Rec. G.241.
[3] CCITT Recommendation Interruption control , Vol. VI,
Rec. Q.416.
[4] CCITT Recommendation Recommendations relating to the
accuracy of carrier frequencies , Vol. III, Rec. G.225.
[5] CCITT Recommendation Signal receiver , Vol. VI,
Rec. Q.415.
[6] CCITT Recommendation Signal sender , Vol. VI,
Rec. Q.414.
[7] CCITT Recommendation Digital line signalling code ,
Vol. VI, Rec. Q.421, S 3.1.2.
[8] CCITT Recommendation Conversion between analogue and
digital versions of system R2 line signalling , Vol. VI,
Rec. Q.430.
[9] CCITT Recommendation Interruption control , Vol. VI,
Rec. Q.416, SS 2.4.3.2 and 2.4.3.3.
[10] CCITT Recommendation Pilots on groups, supergroups,
etc. , Vol. III, Rec. G.241, S 1.
[11] CCITT Recommendation Protection against the effect of
faulty transmission on groups of circuits , Vol. VI, Rec. Q.33.
Recommendation G.794
CHARACTERISTICS OF 24-CHANNEL TRANSMULTIPLEXING EQUIPMENTS
(Malaga-Torremolinos, 1984, amended at Melbourne, 1988)
1 Introduction
The 24-channel transmultiplexer is a transmultiplexing equip-
ment which satisfies Recommendations G.791 and G.792 and provides
interconnection between a digital signal at 1544 kbit/s and two
analogue basic groups (24-channel TMUX-P).
2 Digital interfaces
2.1 Coding law
The coding law used is u-law specified in
Recommendation G.711.
2.2 Interfaces
The 1544 kbit/s interfaces satisfy Recommendation G.703, S 2.
2.3 Frame structure
The 1544 kbit/s frame structure satisfies Recommendation
G.704, S 3.1.1.
2.4 Multiframe structure
The multiframe structure carried on the F-bit satisfies
Recommendation G.704, S 3.1.1.
3 Analogue interfaces
3.1 Ports
The analogue interface consists of two 12-channel groups (band
60-108 kHz) which satisfies Recommendation G.232.
The preferred signal levels at the group distribution frame
satisfy Recommendation G.233.
3.2 Pilots
The 24-channel transmultiplexer should transmit and receive
the group pilot in Recommendation G.241.
3.3 Pilot detection and regulation
The transmultiplexer may or may not regulate levels on the
basis of the levels of the group pilots. If so, the transmulti-
plexer must meet the conditions of Recommendation G.241.
4 Correspondence between analogue and digital channels
A fixed correspondence is established between the analogue and
digital channels. The following correspondence:
PCM 1: Basic group 1
Channels 1 to 12: 60-108 kHz
PCM 1: Basic group 2
Channels 13 to 24: 60-108 kHz
5 Synchronization of transmultiplexer
The transmultiplexer must produce virtual analogue carrier
frequencies with the accuracy specified in Recommendation G.225 (_
| 0DlF2617).
For this purpose, it is recommended:
a) either that the transmultiplexer should have an
internal clock of sufficient accuracy;
b) or that the transmultiplexer should be synchron-
izable with an external signal which may be:
1) a frequency produced by a central generator: 4,
12, 124 kHz;
2) or one of the incoming PCM streams which has
sufficient accuracy (this may be the case, for example when this
PCM stream 1544 kbit/s is produced by a TDM switching equipment).
Note 1 - In the case of a digital filtering transmultiplexer,
when synchronization on the incoming PCM stream is not possible,
the remote digital terminal should have the sending side synchron-
ized with the receiving side so as to avoid slipping at the
transmultiplexer input.
Note 2 - In the case of external synchronization, transmulti-
plexers often have an internal oscillator locked to the external
signal. If, upon loss of the external sync signal, this internal
oscillator is allowed to continue to supply the clock for the out-
going digital signal (now in the free-running mode), then this
oscillator should have a minimum free-running accuracy of
50 x 10DlF2616. This is intended to allow the distant end digital
terminal to receive an adequate frequency for alarm purposes only,
so as not to confuse maintenance and trouble-shooting activities.
Also, a local alarm should be given in the event of a fault in the
synchronization system or in the absence of the external synchroni-
zation signal.
Note 3 - In the case where the transmultiplexer is to be used
in a TDMA satellite application, the effect of the satellite
Doppler frequency variation must be taken into account. This can be
done in two ways:
- either, the TDMA terminal incorporates the
Doppler buffer memories of appropriate capacity in the earth sta-
tion to satellite direction. In this case, the two directions of
the TMUX must be synchronized from one of the two 1544 kbit/s PCM
streams transmitted by the TDMA receive terminal;
- or, the TDMA terminal does not incorporate
Doppler buffers. In this case, the PCM to FDM direction of the TMUX
may be synchronized from one of the two 1544 kbit/s streams
transmitted by the TDMA receive terminal. In the FDM to PCM direc-
tion, the 1544 kbit/s streams transmitted by the TMUX must be made
synchronous with the TDMA system transmit clock: this supposes that
a synchronization signal (contradirectional with the data) is pro-
vided by the TDMA transmit terminal to the TMUX. In the case where
the processing in a digital filtering transmultiplexer is made syn-
chronously for the two directions, Doppler buffer memories of
appropriate capacity must be incorporated in the PCM interfaces.
6 Signalling
Two different approaches can be envisaged:
6.1 No signalling translation in TMUX
This is applicable to applications such as in-band end-to-end
signalling, and common channel signalling such as CCITT No. 6 or
CCITT No. 7.
6.2 Translation of analogue signalling (Recommendation
Q.21) into 1544 kbit/s PCM line signalling (Recommendation G.733)
This translation is applicable to the predominant forms of
analogue and digital signalling recommended by CCITT for interna-
tional circuits (excluding signalling system R2) consisting of
12-channel analogue groups and 1544 kbit/s PCM digital signals.
7 Fault conditions and consequent actions
The principle governing the handling of alarms is as follows:
The behaviour of the 24-channel transmultiplexer vis-a-vis a
24-channel PCM multiplex equipment should be the same as that of
another 24-channel PCM multiplex equipment. Vis-a-vis a channel
translator, it should behave like another channel translator.
Table 1/G.794 summarizes the fault conditions and consequent
actions in accordance with the frame structure, defined in
Recommendation G.704.
Blanc
H.T. [1T1.794]
TABLE 1/G.794
Fault conditions and consequent action for the
24-channel transmultiplexer
_________________________________________________________________________________________________________________________________________________________
{
Consequent
Action
Fault Conditions
} {
Prompt maintenance alarm indication (7)
} {
Alarm indication to the remote equipment (3)
} AIS sending (4) {
Blocking of faulty speech channels
} {
Pilot cut-off
to the remote
FDM terminal
}
{
Loss of frame alignment and multiframe alignment or
Loss of incoming signal (2)
} Yes (8) Yes Yes (PCM | > | DM) {
Digital error
ratio 10DlF2614
or 10DlF2613 (10)
}
_________________________________________________________________________________________________________________________________________________________
Yes (8) Yes {
Reception of alarm indication
from the remote equipment (2, 3)
} Yes AIS receiving (4)
_________________________________________________________________________________________________________________________________________________________
Yes Yes (PCM | | > | DM)
_________________________________________________________________________________________________________________________________________________________
Absence of group pilot (5) Yes Yes (9) Yes {
Pilot level deviation alarm (11)
}
_________________________________________________________________________________________________________________________________________________________
Yes, if regulation is present
_________________________________________________________________________________________________________________________________________________________
Failure of power supply (2) Yes {
Yes, depending
on network
applications
} System failure (6) Yes
_________________________________________________________________________________________________________________________________________________________
{
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} {
Yes, depending
on network
applications
} Synchronization failure Yes
_________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes in the table signifies that an action should be
taken as a consequence of the relevant fault conditions. An open
space in the table signifies that the relevant action should not be
taken as a consequence of the relevant fault condition, if this
condition is the only one present. If more than one fault condition
is simultaneously present, the relevant action should be taken if,
for at least one of the conditions, a Yes is defined in relation to
this action.
Note 2 - The fault conditions "Loss of incoming signal", "Loss of
frame alignment and multiframe alignment", "Reception of alarm
indication to the remote equipment" and "Failure of power supply"
are defined in Recommendation G.733.
Note 3 - For "Alarm indication to the remote equipment", data link
bits are used.
Note 4 - The AIS can be used only in the new frame structure to be
specified by Study Group XVIII.
Note 5 - The level, at which "Absence of group pilot" is detected,
is under study.
Note 6 - The "System failure", which is only for the digital
filtering transmultiplexer, corresponds to a fault detected by the
transmultiplexer's supervision system, when it has one.
Note 7 - The consequent action "Prompt maintenance Alarm indica-
tion" and "Alarm indication to the remote equipment" are defined in
Recommendation G.733.
Tableau 1/G.794 [1T1.794], p. 14
H.T. [2T1.794]
Note 8 - When AIS is detected, the "Prompt maintenance alarm indi-
cation" associated with the "Loss of frame alignment and multiframe
alignment" with the "Loss of incoming signal" or with the "Digital
error ratio 10DlF2614" should be blocked.
Note 9 - The AIS is sent only if the 24 channels of a single PCM
stream are in the alarm condition.
Note 10 - Depends on network applications.
Note 11 - "Pilot level deviation alarm" corresponds to a variation
on the level of the incoming pilot from its nominal value by more
than _ | dB, as stated in CCITT Recommendation G.241, S 1. This
applies only to transmultiplexers with automatic internal level
regulation.
Pour Montage : System alarm FDM alarm PCM alarm
H.T. [T1.795]
FDM codecs
____________________________________________________________________________________
Administration Analogue interface Digital interface Noise performance
____________________________________________________________________________________
British Telecom Supergroup (312-552 kHz) 8 | 48 kbit/s < 140 pW0p
____________________________________________________________________________________
British Telecom {
15 SG assembly
(312-4025 kHz)
} 68 | 36 kbit/s < 700 pW0p
____________________________________________________________________________________
China {
Mastergroup
(812-2044 kHz
or 60-1300 kHz)
} 34 | 68 kbit/s < 783 pW0p
____________________________________________________________________________________
NTT Group (60-108 kHz) 1 | 44 kbit/s < 340 pW0p
____________________________________________________________________________________
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Tableau 1/G.794 [2T1.794], p. 15
Recommendation G.795
CHARACTERISTICS OF CODECS FOR FDM ASSEMBLIES
(Malaga-Torremolinos, 1984, amended at Melbourne, 1988)
The CCITT,
considering
that codecs capable of encoding/decoding FDM assemblies will:
a) be a useful element in the transmission networks
of some Administrations during the period of transition from analo-
gue to digital working;
b) have a limited life and application;
c) already be available in a number of realiza-
tions,
recommends
that FDM codecs should conform with the following require-
ments:
1 General
This Recommendation gives details of the analogue interfaces,
the overall analogue-to-analogue performance of a coder/decoder
pair and certain details of the digital interfaces to which FDM
codecs should conform. The CCITT does not recommend any particular
relationship between FDM assemblies and the digital hierarchies to
be used in any codec realization nor does it recommend any particu-
lar frame structure or encoding law. Administrations intending to
use codecs in their networks should ensure that compatible designs
of codec are used at each end of a link. For international links,
the codecs to be used should be by the agreement of the Administra-
tions concerned. An Annex to this Recommendation gives details sup-
plied by some Administrations of a number of FDM codec realiza-
tions.
The application of FDM codecs in a network is explained in
Supplement No. 28.
2 Analogue interfaces
2.1 FDM assemblies
The constitution of the FDM assemblies at the analogue input
and output should conform to Recommendation G.211, Figure 1 | fIa)
/G.211, for the basic group and Recommendation G.233,
Figures 1/G.233 through 5/G.233, as appropriate for the basic
supergroup, mastergroup, supermastergroup and 15 supergroup assem-
blies.
2.2 Impedances and relative levels
The impedances and relative levels at the analogue transmis-
sion ports should be as indicated in Recommendation G.233, SS 3
through 6.
2.3 Return loss
The return loss against the nominal impedance of all analogue
transmission ports should be at least 20 dB in the wanted frequency
band. This limit relates to the intrinsic return loss, i.e. that is
obtained when the cords connecting the measuring apparatus to the
equipment are as short as possible. In view of the station cabling
encountered in practice, the return loss recorded at the distribu-
tion frame of groups, supergroups, etc., may differ from the
intrinsic return loss. This factor should be taken into account in
designing and making links.
2.4 Accuracy of carrier frequencies
Designers of FDM codecs may find it expedient to translate the
analogue signal frequency before coding and after decoding. The
accuracy of any carrier frequencies used should conform to
Recommendation G.225. It is possible to lock the carriers to the
digital signal so that no overall frequency error is caused by the
FDM codecs.
3 Digital interfaces
Digital interfaces should conform to the appropriate sections
of Recommendation G.703.
4 Encoding law and frame structure
At present the CCITT does not recommend any particular encod-
ing law or frame structure. In some instances it may not be techni-
cally or economically feasible to encode one standardized FDM
assembly into one standardized hierarchical bit rate. In these
cases it is possible that more than one encoded FDM assembly or an
encoded FDM assembly and lower order hierarchical bit streams may
be combined to form one standardized hierarchical bit rate conform-
ing to Recommendation G.703. Where one or several encoded FDM
assemblies are combined with some lower order hierarchical bit
streams, then the multiplexing techniques used must be plesiochro-
nous.
5 Analogue performance
The analogue performance is recommended in terms of the
overall performance of a coder/decoder pair.
5.1 Noise
A maximum value of 800 pW0p is recommended. In practice, this
magnitude of noise is expected to occur only on codecs for the
higher order FDM assemblies and that significantly lower values
will be achieved with codecs for the smaller FDM assemblies (see
the Annex to this Recommendation). The use of FDM codecs on com-
paratively short transmission paths becomes possible when lower
levels of codec noise are achieved. The recommended allowance of
noise is intended to take account of all sources of noise,
i.e. noise due to:
a) analogue processing before the coder and follow-
ing the decoder,
b) quantization,
c) errors and jitter on the received digital signal
as indicated in the G.900 series of Recommendations.
Noise should be measured in accordance with Recommendation
G.230 under the loading conditions given in Recommendation G.222,
S 4, for the particular FDM assembly used (see Note).
Note - The contribution to this noise made by errors on the
digital transmission path is likely to be small. The effect of
errors is to give rise to impulsive type interference and its
expression in pW0p depends upon the statistics of the error distri-
bution. However, for design purposes, it should be assumed that
errors occurring on the digital line system have a Poisson distri-
bution with a long-term mean error ratio of 10DlF2617.
5.2 Performance under conditions of light loading
Under conditions of light loading, the quantizing distortion
caused by a discrete tone (e.g. a test tone or signalling fre-
quency) may give rise to a structured noise spectrum containing
components considerably in excess of the average quantizing distor-
tion level per channel. However, in practice, the presence of a
small number of system reference pilots and carrier leaks is suffi-
cient to maintain an adequately uniform noise spectral distribu-
tion.
5.3 Overload point
Should be as given in Recommendation G.233, S 6 (see Note).
Note - A higher loading is appropriate if digital speech
interpolation techniques or 3 kHz spaced channels
(Recommendation G.235) are used.
5.4 Frequency response
The amplitude/frequency response, the ratio between wanted and
unwanted components and the group delay distortion recommended is
that given in Recommendation G.242 for through connections of the
relevant FDM assemblies. This performance will be adequate to allow
direct connection of the FDM codec analogue ports to the low fre-
quency side of following translating equipment. However, if the
analogue ports of the FDM codec are to be directly connected to the
high frequency side of translating equipment, then the performance
required of the FDM codec may appropriately be that performance
normally required by the Administration of its translating equip-
ment.
5.5 Go-return crosstalk
The go-return crosstalk ratio should not be worse than 80 dB.
This level of crosstalk may be difficult to measure because of
the digital processing in the transmission path. It may be neces-
sary to add to the disturbed path a low level activating signal (a
sine wave or band limited white noise) to avoid gain enhancement
effects.
5.6 Unwanted modulation by harmonics of the power supply
and other low frequencies
The combined effect of a coder/decoder pair should correspond
to a minimum side component attenuation of 57 dB
(Recommendation G.229).
5.7 Phase jitter
The phase jitter on a signal caused by a coder/decoder pair
should not exceed 1 peak-to-peak when measured in the frequency
band given in Recommendation G.229, S 2.
Note - The value quoted above is indicated as guidance for
design purposes. In practical applications, the codec should
tolerate the jitter of the digital interfaces as specified in
Recommendations G.823 and G.824.
6 Fault conditions and consequent actions
The decoder should detect:
a) loss of frame alignment;
b) loss of digital input signal;
c) the presence of Alarm Indication Signal (AIS) on
the digital input port.
For all these conditions, the analogue output signal should be
suppressed.
Note - Other conditions and consequent actions are under
study.
ANNEX A
(to Recommendation G.795)
H.T. [T1.795]
FDM codecs
____________________________________________________________________________________
Administration Analogue interface Digital interface Noise performance
____________________________________________________________________________________
British Telecom Supergroup (312-552 kHz) 8 | 48 kbit/s < 140 pW0p
____________________________________________________________________________________
British Telecom {
15 SG assembly
(312-4025 kHz)
} 68 | 36 kbit/s < 700 pW0p
____________________________________________________________________________________
China {
Mastergroup
(812-2044 kHz
or 60-1300 kHz)
} 34 | 68 kbit/s < 783 pW0p
____________________________________________________________________________________
NTT Group (60-108 kHz) 1 | 44 kbit/s < 340 pW0p
____________________________________________________________________________________
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Table [T1.795], p.
Supplement No. 28
APPLICATION OF TRANSMULTIPLEXERS, FDM CODECS, DATA-IN-VOICE
(DIV) |
SYSTEMS
AND DATA-OVER-VOICE (DOV) SYSTEMS
DURING THE TRANSITION FROM AN ANALOGUE TO A DIGITAL NETWORK
(Referred to in Recommendations G.791 to G.795; this supplement
is to be found on page 397 of Fascicle III.3 of
the Red Book , Geneva, 1985.)
Supplement No. 31
STATUS OF WORK OF PRESENTLY CONSIDERED DIGITAL CIRCUIT
MULTIPLICATION EQUIPMENT (DCME) DOCUMENTS
(Melbourne, 1988)
(referred to in Recommendation G.763)
The intent is to achieve a single comprehensive DCME Recommen-
dation based on the current work of various Administrations, recog-
nized private operating agencies and recognized standards bodies.
Consideration is being given to make the CCITT Recommendation
on DCME applicable to all circumstances where DCME is required
(i.e. cable and satellite, various signalling protocols, etc.). It
will be of such detail that equipment conforming to it, but
obtained from different design sources, would work together satis-
factorily within a single system.
Documents important to the study of a detailed DCME Recommen-
dation (planned and available) include:
INTELSAT - A detailed specification -
INTELSAT earth station standards (IESS) (Document IEES-501 Rev.1)
digital circuit multiplication equipment specification, 32 kbit/s
ADPCM with DSI , (15 March 1988) has been approved and issued by
the INTELSAT Board of Governors.
France - Contribution to Study Group XV,
April 1988, Description of a bearer frame format and associated
assignment channel used in the CELTIC-3G DCMS, and performance
evaluation (which incorporates a 2 bit overload strategy on speech
signals).
EUTELSAT - Detailed EUTELSAT specification
(Document BS14-49), DCME specification, 32 kbit/s ADPCM and DSI ,
May 1988, approved by the EUTELSAT Board of Signatories (Note 1).
Committee T1 - Digital circuit multiplica-
tion equipment interworking standard , under study with draft stan-
dard scheduled for submission for voting at the end of 1988
(Note 2).
Note 1 - This specification is based in a large part on the
INTELSAT specification IESS-501 Rev.1 with modifications and addi-
tions appropriate to the European: countries (particularly R2D sig-
nalling system accomodation).
Note 2 - The current draft is based in large part on the
INTELSAT specification IESS-501, 16 September 1987, with modifica-
tions appropriate to the US national situation.
Supplement No. 32
TRANSFER OF ALARM INFORMATION ON 60-CHANNEL |
TRANSMULTIPLEXING EQUIPMENT
(Melbourne, 1988)
(referred to in Recommendation G.793)
1 Introduction
In the transition period from analogue to digital networks,
interconnection between analogue and digital systems will be neces-
sary. In some cases, transmultiplexing equipment can provide the
necessary interconnection as described in Supplement No. 28 of
Volume III of the Red Book [1].
Due to the different number of channels contained in the vari-
ous FDM assemblies and TDM arrangements in both analogue and digi-
tal hierarchies, the transmission of alarm information may lead to
some difficulties (e.g. blocking of non-faulty channels, etc.) if
no special means are foreseen.
Methods for alarm transfer based on international standardized
signalling systems are already described in Recommendations G.793.
The basic principles are summarized in S 3 below. Other solutions
can be implemented in national networks or in international net-
works by bilateral agreement. Paragraph 4 describes a number of
possible methods used by various Administrations.
2 Principles of transmultiplexing
2.1 Correspondence between FDM and TDM hierarchies (see
Figure 1)
According to Recommendation G.793, the relationship is as
shown in Table 1.
H.T. [T1.32]
TABLE 1
_____________________________________________________
Group Analogue channels PCM PCM channels
_____________________________________________________
1 1 to 12 1 1 to 12
2 1 to 12 1 13 to 24
3 1 to 6 1 25 to 30
3 7 to 12 2 1 to 6
4 1 to 12 2 7 to 18
5 1 to 12 2 19 to 30
_____________________________________________________
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Note - In national networks or by agreement between Administra-
tions, other schemes of correspondence between analogue and digital
channels may be used.
Tableau 1 [T1.32], p. 17
2.2 Detection of fault conditions in transmultiplexers
According to the specification in Rec. G.793, the following
fault conditions are detected in transmultiplexers:
a) digital side
- loss of incoming signal, error ratio greater than
10DlF2613, loss of frame alignment;
- loss of multiframe alignment (when used);
- detection of a remote alarm.
b) analogue side
- loss of group pilot;
- loss of supergroup pilot;
- pilot level deviation alarm.
c) system alarm
- failure of power supply;
- system failure (if in-service monitoring is
implemented);
- synchronization failure.
2.3 Transmission of alarm information (see Figure 1)
a) FDM towards TDM
If one of the group pilots fails, then for the relevant
group an individual alarm should be transmitted from the analogue
side to the relevant digital output port of the transmultiplexer.
In the 60 channel-TMUX, this creates a specific problem in the case
of group 3 , which is split between the two digital streams.
b) TDM towards FDM
In the 60 channel-TMUX, if only one of the two digital
incoming composite streams fails, no group pilot should be sent to
the analogue output port of the transmultiplexer for groups 1 and 2
(or 4 and 5 respectively) and for group 3 where 6 non-faulty chan-
nels might then be out of service (see S 3).
In both cases, some kind of per channel alarm information is
required to solve the difficulties.
3 Alarm transfer based on international standardized signal-
ling systems
When the 2-bit version of Signalling System R2 is used on the
digital side of a TMUX, then a conversion between the digital and
the analogue versions of R2 is performed in the TMUX, according to
Recommendation Q.430. This conversion allows some alarm transfer on
a per-channel basis of the signalling information itself (on the
digital side, bits a and b of time slot 16 are used completely for
signalling). Table 2/G.793 refers to this method.
For in-band signalling and common channel signalling,
Table 3/G.793 gives the fault conditions and consequent actions.
However, the problem of alarm transfer on a per channel basis has
not yet been solved, and is currently being studied by Study
Group XI for supervision of TDMA/DSI satellite systems.
One possibility is to use bits a or b of time slot 16 to
transmit some alarm indication on a per-channel basis from FDM to
PCM, as in the case of the analogue version of S.S.R2 (see S 4.1
below). However, in the opposite direction, when only one PCM
stream fails, it is in principle either possible to block
6 non-faulty channels, or not to block 6 faulty channels. Since in
the latter case subscribers may be charged even though they are not
connected by a speech path, it is preferable to adopt the first
alternative.
Alternative methods of alarm transfer are in use in national
applications and these are described in S 4 below.
Figure 1, p. 18
4 Methods of alarm transfer used in national applications
4.1 Analogue version of Signalling System R2
4.1.1 In national networks, the following arrangements con-
forming to [2] may be used when the circuits connected to the
transmultiplexer are operated with the Signalling System R2.
The 60-channel transmultiplexer establishes a correspondence
between the signalling data carried by time slots 16 of the PCM
frames and the out-of-band signalling frequencies at 3825 Hz. The
specifications concerning these signalling frequencies are con-
tained in Recommendations Q.414 and Q.415.
The signalling bit a associated with a channel is used to
transmit the presence or absence of the signalling frequency in
that channel. The signalling bit b associated with a channel is
used to transmit alarm information to the channel in the FDM to PCM
direction, when the loss of the group pilot carrying the channel is
detected.
In this organization, the principles governing the handling of
alarms is as follows:
- priority is given to the correct functioning of
the interruption control system (Recommendation Q.416);
- the behaviour of a transmultiplexer vis-a-vis a
30 channel PCM multiplex should be the same as that of another
30-channel PCM multiplex. However, the transmultiplexer performs
certain functions peculiar to digital multiplexing equipments, such
as the emission of the AIS. Vis-a-vis a group modulator, it should
behave like another group modulator.
Table 2 summarizes fault conditions and consequent actions.
4.1.2 The same solution may also be used for another national
out-of-band signalling systems.
4.1.3 In some cases, it may be desirable for the transmulti-
plexer to provide locally the information control information
relating to the various groups.
4.2 Other out-of-band signalling systems
The same methods as for the analogue version of Signalling
System R2 can be used. Table 2 also applies.
4.3 Multiframe in combination with inband and common
channel signalling system [3]
4.3.1 Inband signalling (Signalling Systems No. 4 and 5)
In the case of inband signalling, normally no multiframe
alignment exists. Therefore time slot 16 may be used for transmis-
sion of additional signals, e.g. data signals. In this case, there
is no possibility for transmission of pilot-alarms.
If time slot 16 is not used for transmission of additional
signals, bit a or bit b of this time slot can be used for transmis-
sion of pilot-alarms in the FDM PCM direction. In this case, mul-
tiframe alignment is necessary.
In the PCM FDM direction Note 5 of Table 3.
4.3.2 Common channel signalling
The following refers only to Signalling System No. 7. This
system is optimized for operation in digital telecommunication net-
works over 64 kbit/s digital channels (see Rec. Q.701). Therefore,
digital data links should be preferred. But analogue transmission
rates over 4 kHz or 3 kHz channels and modems, e.g. with 2400 bit/s
is also possible (Recs. Q.701, Q.702) if no digital channel is
available.
Low speed signalling data links can be transmitted over a
transmultiplexer. Fault conditions and consequent actions are the
same as for inband signalling. (See Table 3)
H.T. [1T2.32]
_________________________________________________________
TABLE 2
{
Fault conditions and consequent actions, applicable for
national networks where Signalling System R2, 1-bit
analogue version, is used
(see Note 1)
}
_________________________________________________________
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_____________________________________________________________________________________________________________________________________________________________________________________________
Consequent actions
|
Fault conditions {
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 4) Yes Yes PCM | > | DM Yes PCM | > | DM Yes (see Note 5)
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of multitrame alignment (see Note 2)
} Yes (see Note 4) Yes Yes PCM | > | DM Yes (see Note 5)
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Absence of received group pilot
(see Note 6)
} Yes Yes FDM | > | CM Yes FDM | > | CM Yes (see Note 7) Yes (see Notes 3 and 7)
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received supergroup pilot
(see Note 8)
} Yes
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm
(Note 9)
} Yes
_____________________________________________________________________________________________________________________________________________________________________________________________
Failure of poser supply Yes Yes, if possible Yes, if possible
_____________________________________________________________________________________________________________________________________________________________________________________________
{
System failure
(see Note 10)
} Yes Yes, 5 groups Yes (see Note 7) Yes (see Notes 3 and 7)
_____________________________________________________________________________________________________________________________________________________________________________________________
{
Synchronization failure
(see Note 11)
} Yes
_____________________________________________________________________________________________________________________________________________________________________________________________
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Pour Montage : System alarms FDM alarms PCM alarms
Tableau 2 [1T2.32] (a l'italienne), p. 19
H.T. [2T2.32]
Note 1 - A Yes
| n the table signifies, that an action should be taken as a
consequence of the relevant fault conditions. An open space in the
table signifies that the relevant action should not be taken as a
consequence of the relevant fault condition, if this condition is
the only one present. If more than one fault condition is simul-
taneously present, the relevant action should be taken if, for at
least one of the condition, a Yes is defined in relation to this
action.
Note 2 - The fault conditions "Loss of signal at 2 Mbit/s", "Error
ratio > 10DlF2613", "Loss of frame alignment", "Loss of multiframe
alignment" and the consequent action "Bit 3, time slot 0 to 1",
"Bit 6, time slot 16, frame 0 to 1" and "AIS sent" are defined in
Recommendation G.732.
Note 3 - Bits b of time slot 16 are used for channel associated
transmission of the alarm of an individual group pilot of the
affected 12 channels if the FDM PCM direction, so as to ensure
the correct functioning of the interruption control, without having
to suppress channels that are not necessarily faulty, for example,
in the case of a fault on a single group. In the case of group 3,
bits b of the concerned 2x6 channels of the two 2048 kbit/s bit
streams are affected.
Note 4 - The 60-channel transmultiplexer should be able to detect
the Alarm Indication Signal (AIS) on incoming streams at
2048 kbit/s. When AIS is detected, the prompt maintenance indica-
tion associated with the loss of frame alignment, with an excessive
error rate or with the loss of multiframe alignment should be
blocked.
Note 5 - In the PCM FDM direction, the pilots must be cut for the
3 groups associated with a PCM multiplex signal in the event of
the detection of a fault on the PCM multiplex signal stream. When a
single PCM multiplex signal is faulty, this involves the blocking
of 6 channels which are not faulty.
Note 6 - The definition of absence of group pilot used for the
operation of the interruption control system is given in the
Recommendation Q.416, SS 2.4.3.2 and 2.4.3.3. The supergroup pilot
can also be used.
Note 7 - The AIS is sent only if the 30 channels of a single PCM
stream are in the alarm condition. The sending of AIS then has
priority over the setting of bit b of time slot 16 to 1.
Note 8 - Detection of "absence of supergroup pilot" is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Note 9 - The concept of pilot level deviation alarm corresponds to
a variation on the level of the pilot from its nominal value by
more than _ | dB, as stated in Recommendation G.241, S 1. This
applies only to transmultiplexers with automatic internal level
regulation.
Note 10 - The "system" fault condition corresponds to a fault on
the transmultiplexer detected by the transmultiplexer's supervision
system, when it has one.
Note 11 - The "synchronization" fault is that mentionned in S 6 of
Recommendation G.793. When the transmultiplexer is synchronized
with an external signal or with one of the two incoming PCM streams
at 2048 kbit/s, the transmultiplexer should transmit an alarm sig-
nal in the event of synchronization loss.
H.T. [1T3.32]
________________________________________________________________
TABLE 3
{
Fault conditions and consequent sections for inband signalling
systems and common channel
signalling systems with low bit rates
(Note 1)
}
________________________________________________________________
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__________________________________________________________________________________________________________________________________________________________________________
Consequent actions
|
Fault conditions {
__________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 4) Yes Yes PCM > FDM Yes (see Note 5)
__________________________________________________________________________________________________________________________________________________________________________
{
Loss of multiframe alignment
(see Note 2) (optional)
} Yes (see Note 4) Yes Yes (see Note 5)
__________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received group pilot
(see Note 6)
} Yes Yes FDM > PCM Yes (see Note 7) Yes (see Notes 3 and 7)
__________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received supergroup pilot (see Note 8)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm (see Note 9)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
Failure of power supply Yes Yes, if possible Yes, if possible
__________________________________________________________________________________________________________________________________________________________________________
System failure (see Note 10) Yes Yes, 5 groups Yes (see Note 7) Yes (see Notes 3 and 7)
__________________________________________________________________________________________________________________________________________________________________________
{
Synchronization failure
(see Note 11)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
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Note 1 - A Yes
| n the table signifies, that an action should be taken as a
consequence of the relevant fault conditions. An open space in the
table signifies that the relevant action should not be taken as a
consequence of the relevant fault condition, if this condition is
the only one present. If more than one fault condition is simul-
taneously present, the relevant action should be taken if, for at
least one of the conditions, a Yes is defined in relation to this
action.
POUR MONTAGE: System alarms FDM alarms PCM alarms
Remarques du Tableau 2 [2T2.32], p. 20
H.T. [1T3.32]
________________________________________________________________
TABLE 3
{
Fault conditions and consequent sections for inband signalling
systems and common channel
signalling systems with low bit rates
(Note 1)
}
________________________________________________________________
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__________________________________________________________________________________________________________________________________________________________________________
Consequent actions
|
Fault conditions {
__________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
(see Note 2)
} Yes (see Note 4) Yes Yes PCM > FDM Yes (see Note 5)
__________________________________________________________________________________________________________________________________________________________________________
{
Loss of multiframe alignment
(see Note 2) (optional)
} Yes (see Note 4) Yes Yes (see Note 5)
__________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received group pilot
(see Note 6)
} Yes Yes FDM > PCM Yes (see Note 7) Yes (see Notes 3 and 7)
__________________________________________________________________________________________________________________________________________________________________________
{
Absence of the received supergroup pilot (see Note 8)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm (see Note 9)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
Failure of power supply Yes Yes, if possible Yes, if possible
__________________________________________________________________________________________________________________________________________________________________________
System failure (see Note 10) Yes Yes, 5 groups Yes (see Note 7) Yes (see Notes 3 and 7)
__________________________________________________________________________________________________________________________________________________________________________
{
Synchronization failure
(see Note 11)
} Yes
__________________________________________________________________________________________________________________________________________________________________________
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|
Note 1 - A Yes
| n the table signifies, that an action should be taken as a
consequence of the relevant fault conditions. An open space in the
table signifies that the relevant action should not be taken as a
consequence of the relevant fault condition, if this condition is
the only one present. If more than one fault condition is simul-
taneously present, the relevant action should be taken if, for at
least one of the conditions, a Yes is defined in relation to this
action.
POUR MONTAGE: System alarms FDM alarms PCM alarms
Tableau 3 [T3.32] (a l'italienne), p. 21
H.T. [2T3.32]
Note 2 - The fault conditions "Loss of signal at 2 Mbit/s", "Error
ratio > 10DlF2613", "Loss of frame alignment", "Loss of multiframe
alignment" and the consequent action "Bit 3, time slot 0 to 1",
"Bit 6, time slot 16, frame 0 to 1" and "AIS sent" are defined in
Recommendation G.732.
Note 3 - Bits b of time slot 16 are used for channel associated
transmission of the alarm of an individual group pilot of the
affected 12 channels if the FDM PCM direction, so as to ensure
the correct functioning of the interruption control, without having
to suppress channels that are not necessarily faulty, for example,
in the case of a fault on a single group. In the case of group 3,
bits b of the concerned 2x6 channels of the two 2048 kbit/s bit
streams are affected.
Note 4 - The 60-channel transmultiplexer should be able to detect
the Alarm Indication Signal (AIS) on incoming streams at
2048 kbit/s. When AIS is detected, the prompt maintenance indica-
tion associated with the loss of frame alignment, with an excessive
error rate or with the loss of multiframe alignment should be
blocked.
Note 5 - In the PCM FDM direction, the pilots must be cut for the
3 groups associated with a PCM multiplex signal in the event of
the detection of a fault on the PCM multiplex signal stream. When a
single PCM multiplex signal is faulty, this involves the blocking
of 6 channels which are not faulty.
Note 6 - The definition of absence of group pilot used for the
operation of the interruption control system is given in the
Recommendation Q.416, SS 2.4.3.2 and 2.4.3.3. The supergroup pilot
can also be used.
Note 7 - The AIS is sent only if the 30 channels of a single PCM
stream are in the alarm condition. The sending of AIS then has
priority over the setting of bit b of time slot 16 to 1.
Note 8 - Detection of "absence of supergroup pilot" is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Note 9 - The concept of pilot level deviation alarm corresponds to
a variation on the level of the pilot from its nominal value by
more than _ | dB, as stated in Recommendation G.241, S 1. This
applies only to transmultiplexers with automatic internal level
regulation.
Note 10 - The "system" fault condition corresponds to a fault on
the transmultiplexer detected by the transmultiplexer's supervision
system, when it has one.
Note 11 - The "synchronization" fault is that mentionned in S 6 of
the Recommendation G.793. When the transmultiplexer is synchron-
ized with an external signal or with one of the two incoming PCM
streams at 2048 kbit/s, the transmultiplexer should transmit an
alarm signal in the event of synchronization loss.
H.T. [1T4.32]
____________________________________________________________
TABLE 4
{
Fault conditions and consequent actions for common channel
signalling using combinations
of cut group pilots
(Note 1)
}
____________________________________________________________
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____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
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Pilot cut out
1 2 3 4 5 Suppress supergroup pilot {
{
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
} PCM 1 (Note 2) Yes Yes Yes Yes PCM | > | DM Yes (Note 3)
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
} PCM 2 (Note 2) Yes Yes Yes Yes PCM | > | DM Yes (Note 3) |
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____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of 64 kbit/s PCM 1 input
(Note 4)
} Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of 64 kbit/s PCM 2 input
(Note 4)
} Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Bit 3, time slot 0: PCM 1 Yes Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Bit 3, time slot 0: PCM 2
} Yes Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of Group 1 and Group 2
but not Group 3
} Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Any other combination of Group 1, 2 and 3 losses
} Yes Yes Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of Group 4 and Group 5
but not Group 3
} Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Any other combination of Group 3, 4 and 5 losses
} Yes Yes Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of supergroup pilot (Note 5)
} Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm
(Note 6)
} Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
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Remarques du Tableau 3 [2T3.32] + Remarques, p. 22
4.4 Fault conditions and consequent actions for common
channel signalling using combinations of cut group pilots
The alarm transfer procedure detailed in Table 4 is used in a
TMUX-TMUX and a TMUX-GTE/CTE/PCM MUX link used by BT (United King-
dom). Figure 2 shows how these two types of link are implemented.
The method uses combinations of cut group pilots to transfer stan-
dard digital alarms across the analogue portion of the link. One
pilot is cut to signal a forward alarm and two pilots are cut to
signal a backward alarm. The FDM path is thus effectively tran-
sparent to digital alarms, giving consistency with systems which
are entirely digital. Key features of this method are that it does
not require that alarms be transferred on a per-channel basis and
it ensures that all faulty channels are blocked. It therefore
avoids the problems mentioned in S 3 above.
No modifications are required to the implementation of the
common channel signalling system. The 64 kbit/s common channel sig-
nalling channel is extracted from PCM 1 or PCM 2 and sent over one
group via a modem.
Blanc
Figure 2, p. 23
H.T. [1T4.32]
____________________________________________________________
TABLE 4
{
Fault conditions and consequent actions for common channel
signalling using combinations
of cut group pilots
(Note 1)
}
____________________________________________________________
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____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
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Pilot cut out
1 2 3 4 5 Suppress supergroup pilot {
{
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
} PCM 1 (Note 2) Yes Yes Yes Yes PCM | > | DM Yes (Note 3)
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of signal
Error ratio > 10DlF2613
Loss of frame alignment
} PCM 2 (Note 2) Yes Yes Yes Yes PCM | > | DM Yes (Note 3) |
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____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of 64 kbit/s PCM 1 input
(Note 4)
} Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of 64 kbit/s PCM 2 input
(Note 4)
} Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Bit 3, time slot 0: PCM 1 Yes Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Bit 3, time slot 0: PCM 2
} Yes Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of Group 1 and Group 2
but not Group 3
} Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Any other combination of Group 1, 2 and 3 losses
} Yes Yes Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of Group 4 and Group 5
but not Group 3
} Yes Optional
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Any other combination of Group 3, 4 and 5 losses
} Yes Yes Yes Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Loss of supergroup pilot (Note 5)
} Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Pilot level deviation alarm
(Note 6)
} Yes
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
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Tableau 4 [1T4.32] (a l'italienne), p. 24
H.T. [2T4.32]
_________________________________________________
TABLE 4 (cont.)
_________________________________________________
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_
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Pilot cut out
1 2 3 4 5 Suppress supergroup pilot {
{
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_
Failure of power supply If possible If possible If possible If possible If possible If possible Yes
_
System failure (Note 7) Yes Yes Yes Yes Yes Yes Yes Yes Yes If possible Yes
_
{
Synchronization failure (Note 8)
} Yes Yes Yes Yes Yes Yes Yes Yes Yes If possible Yes
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Note 1 - A Yes
| n the table signifies, that an action should be taken as a
consequence of the relevant fault conditions. An open space in the
table signifies that the relevant action should not be taken as a
consequence of the relevant fault condition, if this condition is
the only one present. If more than one fault condition is simul-
taneously present, the relevant action should be taken if, for at
least one of the conditions, a Yes is defined in relation to this
action.
Note 2 - The fault conditions "Loss of signal", "Error ratio
> 10DlF2613", "Loss of frame alignment", "Loss of multiframe align-
ment" and the consequent action "Bit 3, time slot 0 to 1", and "AIS
sent" are defined in Recommendation G.732.
Note 3 - The TMUX should be able to detect the alarm indication
signal (AIS) on incoming streams at 2048 kbit/s. When AIS is
detected, the prompt maintenance indication associated with the
loss of frame alignment and/or an excessive error ratio should be
blocked.
Note 4 - For transmultiplexers not required to handle common chan-
nel signalling, in either or both PCM streams, it shall be possible
to program the TMUX to suppress the alarms associated with these
fault conditions.
Note 5 - Detection of absence of supergroup pilot is not obliga-
tory. If the supergroup pilot is not sent, this alarm function can
be performed by supervision of the 5 group pilots.
Note 6 - The concept of pilot level deviation alarm corresponds to
a variation on the level of the pilot from its nominal value by
more than _ | dB as stated in Recommandation G.241, S 1. This
applies only to transmultiplexers with automatic internal level
regulation.
Note 7 - The "system" fault condition corresponds to a fault on
the transmultiplexer detected by the transmultiplexer's supervision
system, when it has one.
Note 8 - The "synchronisation" fault is that mentioned in S 6 of
Recommendation G.793. When the transmultiplexer is synchronized
with an external signal or with one of the two incoming PCM streams
at 2048 kbit/s, the transmultiplexer should transmit an alarm sig-
nal in the event of synchronisation loss.
Pour Montage : FDM alarms PCM alarms System alarms
Remarques du Tableau 4 [2T4.32], p. 25
References
[1] Supplement No. 28 Applications of transmultiplexers,
FDM Codecs, data-in-voice (DIV) systems and data-over-voice (DOV)
systems during the transition from an analogue to a digital network
, Red Book, Vol. III.3, Geneva, 1985.
[2] Supplement No. 3 Use of the analogue line signalling
version on 2048 kbit/s PCM transmission systems , Blue Book,
Vol. VI, Fascicle VI.4.
[3] Contribution COM XV-29 (Federal Republic of Germany),
Study Period 1985-88.
[4] Contribution COM XV-58 (United Kingdom), Study Period
1985-88.